Apparatus and control for hot water process



Sept. 22, 1970 APPARATUS Filed Nov. 20, 1967 BITUMINOUS TAR SANDS WATERAND STEAM CONDITIONING DRUM SCREEN I 4 s I \0vERs|zE J. B. GRAYBILL ETALAND CONTROL FOR HOT WATER PROCESS 2 Sheets-Sheet 1 DILUENT COMBINEDFROTH PRIMARY FROTH gg RIFUGE 34 BIITUMEN PRODUCT SETTLED SCAVENGERSCAVENGER FROTH\ 4 I 24 1 O-22 WATER SEPARATION zomz SUMP MIDDLINGS '25SAND mums FIGUREI OIL- RICH MIDDLINGS AIR FLO TATION ZONE OIL-LEANMIDDLINGS l9 DENSITOMETER SAMPLE CELL SCAVENGER pt- 22, 1970 J. B.GRAYBILL ETAL 3,530,042

APPARATUS AND CONTROL FOR HOT WATER PROCESS Filed NOV. 20, 1967' 2Shets-Sheet 2 FIGURE 2 I INVENTORS JAMES B; GRAYBILL CHESTER N; WHITEJUNIOR w; LOVELAND bMM TTORNEY United States Patent US. Cl. 19614.52 6Claims ABSTRACT OF THE DISCLOSURE This invention relates to an apparatusand method for controlling the hot water process for the treatment oftar sands. The improvement in the process comprises introducing aportion of separation cell middlings into a sampling system, settlingthe middlings in the system, measuring the density of the settledmiddlings, and regu lating the water entering and leaving the processseparation zone in response to these measurements so as to control theviscosity of the middlings in the zone. The apparatus used forcontrolling the viscosity of the middlings comprises a sample cell, adensity sensing device, and regulating means responsively connected tothe sensing device to control the water withdrawn from the separationzone.

This invention relates to an apparatus for controlling the hot waterprocess for the treatment of tar sands. Large deposits of these sandsare found as the Athabasca deposits in northern Alberta, Canada. Theevaluated portion of these deposits occupies about five and one-halfmillion acres and is buried by zero to 2000 feet of overburden. It hasbeen estimated that these deposits consist of about 600 billion barrelsof reserves in place, more than 350 billion barrels of recoverablereserves of raw tar sand oil and more than 250 billion barrels ofupgraded synthetic crude oil.

The tar sands are primarily composed of a fine quartz sand having aparticle size greater than that passing a 325 mesh screen. The quartzsand is impregnated with a viscous bitumen in quantities of from to 21weight percent of the total composition. More typically the bitumencontent is from 8 to percent. This bitumen is quite viscous 6 to 8 APIgravityand contains typically 4.5 percent sulfur and 38 percentaromatics. Its specific gravity at F. ranges typically from about 1.00to about 1.06. In addition to the bitumen and quartz sand, the tar sandscontain clay and silt in quantities of from 1 to 50 weight percent ofthe total composition. Silt is normally defined as material which willpass a 325 mesh screen but which is larger than 2 microns. Clay ismaterial smaller than 2 microns including some siliceous ma terial ofthat size.

Several basic extraction methods have been known for many years for theseparation of bitumen from the sands. In the so-called cold watermethod, the separation is accomplished by mixing the sands with asolvent capable of dissolving the bitumen constituent. The mixture isthen introduced into a large volume of water, water with a surface agentadded, or a solution of a neutral salt in water. The combined mass isthen subjected to a pressure or gravity separation.

In the hot water method, the bituminous sands are jetted with steam andmulled with a minor amount of hot water at temperatures in the range ofto 210 F. The resulting pulp is dropped into a stream of circulating hotwater and carried to a separation cell maintained at a temperature ofabout to 200 F. In the separation cell, sand settles to the bottom astailings and bitumen portion of the middlings from a hot ice rises tothe top in the form of an oil froth. An aqueous middlings layercontaining some mineral and bitumen is formed between these layers. Ascavenger step may be conducted on the middlings layer from the primaryseparation step to recover additional amounts of bitumen therefrom. Thisstep usually comprises aerating the middlings as taught by K. A. Clark,The Hot Water Washing Method, Canadian Oil and Gas Industries, 3, 46(1950). These froths can be combined, diluted with naphtha andcentrifuged to remove: more water and residual mineral. The naphtha isthen distilled otf and the bitumen is coked to a high quality crudesuitable for further processing.

The present invention relates to an apparatus and process forcontrolling the operation of the hot water process set out in Floyd etal., U.S. patent application Ser. No. 509,589. Floyd et a1. (now US.Pat. No. 3,401,110, issued Sept. 10, 1968) teach a hot water process forrecovering additional bitumen in which the water incorporated with thebituminous sands for discharge into the separation cell and the rate ofpassage of the middlings from the separation cell to the scavenger stepare both regulated in order to maintain the density of the middlingslayer within the range of 1.03 to 1.50 and/or the viscosity of themiddlings within the range of 0.56 to 10 centipoises.

The present invention relates to a means for controlling the process ofFloyd et al. Floyd et .al. point out that bitumen froth recovery isaffected by control of the viscosity of the middlings within a specifiedrange. It has now been found that the viscosity of the middlings shouldbe maintained within the range of about 0.4 to about 5.7 centipoisesmeasured at F. with typical operation at about 1 to 2 centipoises at 190F. As Floyd et al. point out, the viscosity is relatable to middlingsclay content which can be maintained by regulating the amount waterincorporated with the bituminous sands in an initial pulp forming stageand the rate of passage of the middlings from the separation cell to thescavenger step. It has now been found that middlings clay content isrelatable to the settled density of the middlings where settled densityis defined as measured density determined when mineral material whichwill not pass a 325 mesh screen has substantially settled out from themiddlings sample. The viscosity of the middlings in the separation cellcan be maintained within the desired range of about 0.4 to 5.7centipoises by regulating the clay content of the middlings bymaintaining the settled density of the middlings within the range ofabout 1.03 to 1.09 g./ml.

The present invention relates to a system for measuring the settleddensity of the separation cell middlings and for regulating water feedrates to the process in response to these measurements. Providing such asystem poses a unique problem for the following reasons: (1) thecomposition of the material being handled is unique; (2) accuracy andspeed of measurement are required; and (3) the response to thesemeasurements must be reliable in order to smoothly control scavengercell feed.

The middlings dragstream on which the measurements are to be run istypically comprised of about 1 to 5 weight percent bitumen, and 20 to 35weight percent total mineral of which about 1 to 3 percent is clay. Thedensity of the dragstream settled is typically between about 1.05 and1.07 g./ml. at 190 F.

The process of this invention comprises introducing a water processseparation cell into a sampling system. In the sampling system entrainedsand is substantially removed by settling from the portion of the samplewhich is to be analyzed. The density of the sample is measured as thesample settles and the water incorporated into the tar sands and thestream to the scavenger zone from the separation cell are regulated inresponse to the measurement so as to maintain the viscosity of themiddlings in the separation cell within the range of 0.4 to 5.7centipoises or preferably about 1 to 2 centipoises.

The process of this invention may be best described with reference tothe drawings. FIG. 1 shows a flow sheet of the hot water processutilizing the improved middlings control system of the presentinvention. FIG. 2 is a schematic representation of the particularapparatus used in the control system.

In FIG. 1, bituminous tar sands are fed into the system through line 1where they first pass to a conditioning drum or muller 3. Water andsteam are introduced from 2 and mixed with the sands. The total water sointroduced is a minor amount based on the weight of the tar sandsprocessed and generally is in the range of 10 to 45 percent by weight ofthe mulled mixture. Enough steam is introduced to raise the temperaturein the conditioning drum to within the range of 130 to 210 F. andpreferably to above 170 F.

An alkali metal-containing alkaline reagent can also be added to theconditioning drum usually in amount of from 0.1 to 3.0 lbs. per ton oftar sand. The amount of such alkaline reagent preferably is regulated tomaintain the pH of the middlings layer in the separator zone within therange 7.5 to 9.0. Best results seem to be obtained at a pH value of 8.0to 8.5. The amount of the alkaline reagent that needs to be added tomaintain a pH value in the range of 7.5 to 9.0 may vary from time totime as the composition of the tar sands as obtained from the mine sitevaries. The best alkaline reagents to use for this purpose are causticsoda, sodium carbonate or sodium silicate, although any of the otheralkali metal'containing alkaline reagents can be used if desired.

lVIulling of the tar sands produces a pulp which then passes from theconditioning drum as indicated by line 4 to a screen indicated at 5. Thepurpose of screen 5 is to remove from the tar sand pulp any debris,rocks or oversized lumps as indicated generally at 6. The pulp thenpasses from screen 5 as indicated by 7 to a sump 8 where it is dilutedwith additional water from 9 and a middlings recycle stream 10. Thisrecycle stream serves to provide suflicient liquid to make the tar sandspulp pumpable so that it can be transferred to the separator.

Modifications that may be made in the process as above described includesending a minor portion of the middlings recycle stream from line 10through a suitable line (not shown) to the conditioning drum to supplyall or a part of the water needed therein other than that suppliedthrough condensation of the steam which is consumed. Also, if desired, astream of the middlings recycle can be introduced onto the screen 5 toflush the pulp therethrough and into the sump. As a general rule thetotal amount of water added to the natural bituminous sands as liquidwater and as steam prior to the separation step should be in the rangeof 0.2 to 3.0 tons per ton of the bituminous sands. The amount of waterneeded within this range increases as the split clay content of thebituminous sands increases. For example, when percent by weight of themineral matter of the tar sands has a particle size below 44 microns,the fresh water added generally can be about 0.3 to 0.5 ton per ton oftar sands. On the other hand, when 30 percent of the mineral matter isbelow 44 microns diameter, generally 0.7 to 10 tons of water should beused per ton of tar sands.

With further reference to FIG. 1, the pulped and diluted tar sands arepumped from the sump 8 through line 11 into the separation cell 12. Thecell contains a relatively quiescent body of hot water which allows forthe formation of a bitumen froth which rises to the cell top and iswithdrawn via line 13 and a sand tailings which settles to the bottom tobe withdrawn through line 14. An aqueous middlings layer between thefroth and tailings layer contains silt and clay and some bitumen whichfailed to form froth. Since suflicient clay is not removed in the sandtailings withdrawn from the bottom of the separation cell through line14 in order to prevent the buildup of clay in the system it is necessaryto continually remove some of the middlings layer and supply enoughwater in the conditioning operations to compensate for that so removed.The rate at which the middlings need to be removed from the systemdepends upon the content of clay and silt present in the tar sands feedand this will vary from time to time as the content of these finesvaries. If the clay and silt content is allowed to build up in thesystem, the viscosity of the middlings layer will increases.Concurrently with such increase an increase in the proportions of boththe bitumen and the sand retained by the middlings will occur. If theclay and silt content is allowed to build up too high in the system,effective separation no longer will occur and the process will becomeinoperative. This is avoided by regulating the recycling and withdrawalof middlings and input of fresh water per the present invention. Evenwhen the separation step is operating properly the middlings layerwithdrawn through line 15 will contain a substantial amount of bitumenwhich did not separate. Hence the middlings layer withdrawn through line15 is, for purpose of description, herein referred to as oil-rich orbitumenrich middlings.

The amount of bitumen removed in the oil-rich middlings layer is relatedto the percentage of clay and/0r silt present in the tar sands beingprocessed, varying directly with the amount of clay and/ or siltpresent. For example, typical bitument recovery values for primary frothfrom tar sands in which 15 percent of the mineral matter is less than 44microns and from sands in which 25 to 30 percent is less than this sizeare respectively percent and 60 percent. For commercial operation it ishighly desirable to obtain increased froth yield in the separation zoneover such vanes as those which are obtainable heretofore by the hotwater process. This is particularly true when the tar sands as minedcontain a relatively high proportion of clay and silt components.

The bitumen-rich middlings stream withdrawn from the separator 12through line 15 is sent to a scavenger zone 16 wherein an air flotationoperation is conducted to cause the formation of additional bitumenfroth. A sample of the middlings is withdrawn from the separation cell12 and is conducted via line 17 to a sample cell 18.

In the sample cell 18 sand is allowed to settle from the sample and asettled density measurement is taken by means of the densitometer 19.The densitometer 19 controls variable speed pump 20 on line 15 so thatif the settled density of the sample withdrawn from the separation cell12 registers above the range 1.03 to 1.09, lead 21 increases thevariable speed pump 20 thereby increasing the flow in line 15 to thescavenger cell 16. Increased flow to the scavenger cell 16 lowers theinterface level between the middlings and froth in the separation cell12. The lowering of the interface level actuates float valve 22 which bymeans of lead 23 opens valve 24 thus increasing the flow of fresh wateraddition to the sump 8 via line 9. Increased water flow through line 9results in increased water content in the diluted pulp passing from thesump 8 through line 11 to the separation cell 12. Flow through pump 25is decreased via lead 26 which responds to the increase in water in thediluted pulp thereby resulting in a reduction in the amount of middlingsrecycle diluting the separation cell feed via 10. Thereby the proportionof fresh water in the separation cell 12 is increased, bringing about adecrease in middlings density. Corre spondingly, if the settled densityof the sample withdrawn via line 17 registers below the operation rangeof 1.03 to 1.09, lead 21 decreases the variable speed pump 20 therebydecreasing the flow in line 15 to the scavenger cell 16. Decreased flowto the scavenger cell raises the interface level in the separation cell12. A raising of the interface level actuates float valve 22 which bymeans of lead 23 closing valve 24 thus decreasing the flow of freshwater addition to the sump via line 9. Decreased water flow through line9 results in decreased water content in the diluted pulp passing fromthe sump 8 through line 11 to the separation cell 12. Flow through pump25 is increased via lead 26 which responds to the decrease in Water inthe diluted pulp in 11 thereby resulting in an increase in the amount ofmiddlings recycle diluting the separation cell feed. Thus the proportionof fresh water in the separation cell 12 is decreased bringing about anincrease in middlings density. The system can be operated so as tomaintain the middlings density within the preferred range of 1.05 to1.07 instead of the broad range as described supra.

Following the process further, in the scavenger zone 16 an air flotationis conducted by any of the air flotation procedures conventionallyutilized in processing of ores. This involves providing a controlledzone of aeration in the flotation cell at a locus where agitation of themiddlings is being elfected so that air becomes dispersed in themiddlings in the form of small bubbles. The drawing illustrates aflotation cell of the sub-aeration type wherein a motorized rotaryagitator is provided and air is fed thereto in controlled amounts.Alternatively the air can be sucked in through the shaft of the rotor.The rotor effects dispersion of the air in the middlings. This aircauses the formation of additional bitumen froth which passes from thescavenger zone 16 through line 27 to a froth settler zone 28. Anoil-lean middlings stream is removed and discarded from the bottom ofthe scavenger zone via line 29.

In the settler zone 28, the scavenger froth forms into a lower layer ofsettler tailings which is withdrawn and recycled via line 30 to be mixedwith bitumen-rich middlings for feed to the scavenger zone 16 via line15. In the settler zone 28 an upper layer of upgraded bitumen frothforms above the tailings and is withdrawn through line 31 and mixed withprimary froth from line 13 for further processing.

The combined froths are at a temperature of about 160 F. They are heatedwith steam and diluted with sulficient naphtha or other diluent from 32to reduce the viscosity of the bitumen for centrifuging in zone 33 toproduce a bitumen product 34 suitable for further processing.

Referring again to the drawings, FIG. 2 schematically illustrates theapparatus and system of the present invention. FIG. 2 shows theapparatus and system utilizing a radiation density gauge but it shouldbe noted that any density sensing device can be used in the presentinvention in place of the radiation gauge. The apparatus consists of asampler cell 18 which in the drawing is a vertical standpipe. Thesampler is located adjacent to the hot water process middlingsseparation cell 12 (not shown) and is connected thereto by a line 17,which is equipped with an inlet valve 35. The sampler standpipe 18 isequipped with an outlet valve 36 and an emergency overflow drain line37. A density sensing and measuring means is located at the top of thesampler as generally indicated by 19 in FIG. 1. In FIG. 2 this meansconsists of a radiation density gauge comprising a radiation source 38,a radiation measuring means 39 and an amplifier, indicator and recorderindicated at 40. This amplifier, indicator and recorder 40 control valve20 of FIG. 1 via lead 21. A float valve 41 is located within the upperstandpipe 18. This float valve 41 is responsive to the liquid level inthe pipe. When the liquid reaches a certain level the valve actuates afloat switch 42 which closes valve 35 stopping middlings flow. in 17from the separation cell.

The operation of the particular apparatus shown in FIG. 2 is describedas follows:

Valve 35 opens and allows a middlings sample to flow from the separationcell 12 via line 17 to the sampler 18. The sample is fed into thesampler standpipe 18 where it is trapped and allowed to settle. When theliquid fills the standpipe 18 it raises the float valve which actuatesthe float switch 42 which then closes the input valve 35 stopping sampleflow from the separation cell. Settled density is then measured by meansof the. density sensing means indicated by 38, 39 and 40 describedsupra. The density amplifier, indicator and recorder 40 then actuatesvalve 20 (shown in FIG. 1) by means of lead 21 as described supra.Settled density is read batchwise for the elapse of each cycle. Thebottom outlet valve 36 is then opened and the sample is dumped. Thecycle is then repeated. If the input valve 35 should fail to close orthe bottom valve fail to open, excess sample would flow from the sampler18 via the emergency overflow line 37.

As mentioned supra the drawing, FIG. 2, shows the apparatus and systemof the present invention utilizing a radiation density gauge. This gaugeis the preferred density measuring device for this apparatus but otherdevices can be used in the invention. The operation of the radiationdensity detector shown will be described in more detail.

The source unit 38 contains a radiation emitting substance such as theradioisotope cesium 137 which emits gamma rays. The source holder isdesigned so that the rays enter the sample as a beam of parallel rays.The ease with which the rays from a given source penetrate a solid orliquid depends upon the density of the material; the more dense thematerial the less the penetration. As the fines content of the middlingssample increases, its density increases and this increase in densitydecreases the intensity of the radiation reaching the measuring cell 39which is situated on the standpipe 18 opposite the radioactive source.If the fines content of the middlings decreases, its settled densitydecreases and the radiation reaching the measuring cell 39 increases.

The measuring cell 39 functions to detect the quantity of radiationpenetrating the standpipe and sample. The radioactive energy istranslated to electrical energy which is transmited to the remoteamplifier, indicator and recorder 40. Here the electrical signal from.the measuring cell is amplified to operate a meter to provide visualindications of sample settled density. A recorder connection can also beprovided on the amplifier-indicator.

Viscosity control of separation cell middlings can be maintained bymanual adjustment of valve 20 as indicated by the density meter on theamplifier 40. However it is preferred to operate this valveautomatically according to settled density readings. The settled densitymeasurements are made batchwise and provide an intermittent electricalsignal representing density. As such this signal is not best suited forautomatic control purposes. A memory unit can be provided as part of thedensity sensing means to hold the signal from one batch measurement onover to the next measurement to provide a smooth constant control on thevalve 20 via lead 21 to provide middlings viscosity control.

What is claimed is:

1. An apparatus for measuring settled density of the middlings in a hotwater process separation zone which comprises:

(a) a sample cell comprising a vertical cell, provided with a dischargeoutlet at the bottom of said cell and a feed inlet at the side of saidcell connected to said separation zone for feeding a middlings samplefrom said zone to said cell; a weir box positioned at the top of saidcell to collect overflow from said cell; a float valve positioned insaid weir box; a float switch responsively attached to said float valveso that said valve actuates said switch when said valve is raised to anupper position in said weir box; and an inlet valve located on said feedinlet and responsively connected to said float switch to close whenactuated by said switch when said switch is actuated by said floatvalve;

(b) a density sensing device located on said sample cell for measuringthe density of a settled middlings sample contained in said cell; and

(c) regulating means responsively connected to said density sensingdevice to control the withdrawal of a stream of middlings from saidseparation zone.

2. The apparatus of claim 1 in Which said density sensing devicecomprises a radiation density detector comprising a radiation source, aradiation measuring means positioned with respect to the said source tomeasure radiation from said source and an amplifier, indicator andrecorder unit connected to said measuring means to translate radiationmeasurements to electrical energy which actuates said regulating means(c).

3. In a system for conducting a hot water process for treating tar sandscomprising a conditioning drum; a separation cell; a first line forsuppling tar sands pulp from said conditioning drum to said separationcell; a second line for introducing hot water into tar sands pulp insaid first line; a third line for withdrawing a bitumen froth productfrom said cell; a fourth line for withdrawing a sand tailings layer fromsaid cell; a fifth line for withdrawing a middlings portion from saidcell; a sixth line for recycling a middlings portion from said cell tobe mixed with said tar sand pulp prior to discharge into said cell; theimprovement which comprises:

(a) a sampling device for withdrawing a sample of middlings from saidcell to measure settled density thereof comprising a vertical cellprovided with a discharge outlet at the bottom of said vertical cell anda feed inlet at the side of said vertical cell connected to saidseparation zone for feeding a middlings sample from said zone to saidvertical cell; a weir box positioned at the top of said cell to collectoverflow from said cell; a float valve positioned in said Weir box; afloat switch responsively attached to said float valve so that saidvalve actuates said switch when said valve is raised to an upperposition in said weir box; and an inlet valve located on said feed inletand responsively connected to said float switch to close when actuatedby said switch when said switch is actuated by said float valve;

('b) a density sensing device connected to said sampling device formeasuring the settled density of said sample;

(c) regulating means controllably attached to said fifth line, andresponsively connected to said density sensing device to control themiddlings portion withdrawn via said fifth line;

(d) regulating means operating in response to said middlings withdrawnin said fifth line and connected to said second line to control the hotwater intro- 8 duced to the bituminous tar sands pulp via said secondline; and

(e) regulating means operating in response to said hot waterincorporated in said second line and connected to said sixth line tocontrol the middlings portion recycled to the bituminous tar sands pulpvia said second line.

4. The system of claim 3 in which said density sensing device (b)comprises a radiation density detector comprising a radiation source, aradiation measuring means positioned with respect to the said source tomeasure radiation from said source and an amplifier, indicator andrecorder unit connected to said measuring means to translate radiationmeasurements to electrical energy which actuated said regulating means(c) and (d).

5. The system of claim 3 in which said regulating means (c) isresponsively connected to said density sensing device so as to increasethe viscosity of said middlings in' said separation cell when saidmiddlings viscosity is below 0.4 centipoise and so as to decrease theviscosity of said middlings in said separation cell when said middlingsviscosity is above 5.7 centipoises.

6. The system of claim 3 in which said regulating means (c) isresponsively connected to said density sensing device so as to increasethe viscosity of said middlings in said separation cell when saidsettled middlings density is below 1.03 g./ml. and so as to decrease theviscosity of said middlings in said separation cell when said settledmiddlings density is above 1.09 g./ml.

- References Cited UNITED STATES PATENTS 2,903,407 9/1959 Fischer et a1.208-11 3,004,544 10/1961 Guptill 137-1 3,009,359 11/1961 Hubby 73-4383,014,362 12/1961 True et a1. 73-53 3,161,203 12/1964 Hathorn et a1137-91 3,229,503 1/1966 Poole et al. 73-32 3,246,145 4/1966 Higgins250-435 3,255,881 6/1966 Holderreed et al. 250-435 3,401,110 9/1968Floyd 208 11 FOREIGN PATENTS 985,097 3/1965 Great Britain.

PAUL M. COUGHLAN, ]R., Primary Examiner T. H. YOUNG, Assistant ExaminerUS. Cl. X.R.

